1. Field of the Invention
The present invention relates to a gas ejection valve for ejecting contents filled in a gas container through a propellant or high-pressure gas such as liquefied CO2 gas. More particularly, the present invention relates to an improved gas ejection valve that is free from leakage of gas with time.
2. Description of the Related Art
There have been used apparatus for ejecting by means of the gas pressure contents such as chemical agent filled, together with high-pressure gas, in a gas container through a gas ejection valve secured to an opening of the gas container. Such ejection apparatus have adopted Freon (CFC) as a propellant, but currently tend to use Freon substitute (for example, HFC134a) in place of Freon as a result of the rise of interest in environmental protection.
Although Freon substitute has no influence on the ozone layer, it causes global warming more than 1,000 times as much as CO2. It is thus predicted that a future increase in its usage may raise a new problem. Therefore, in these days, it is considered to adopt, as a propellant for ejection apparatus, CO2 gas, nitrogen gas, or inert gas such as helium, neon, krypton, xenon or radon that causes less destruction of the ozone layer and influence on global warming.
When using one of the above gases as a propellant for ejection apparatus, it is desirable to reduce the size of a gas container by liquefaction of gas as is carried out for currently-used Freon. For example, the vapor pressure of liquefied CO2 gas is 60 Kgf/cm2 at 20xc2x0 C. Similarly, inert gas is preferably highly compressed or liquefied to achieve increased volume efficiency, the desirable pressure of which is 50 kgf/cm2 or more.
A gas ejection valve applied for such high-pressure gases is disclosed, for example, in JP-A 8-141450. This gas ejection valve comprises a valve casing secured to an opening of a gas container, and a valve pin protrudably held by the valve casing for opening and closing a gas passage through operation from the outside of the gas container. The valve pin has a large-diameter portion that is in close contact with an inner peripheral seal ring arranged in the valve casing, and a small-diameter portion that protrudes upward from the large-diameter portion via a tapered portion. In the steady state with the valve pin being not pushed down, the gas passage is held closed by the large-diameter portion coming in close contact with the inner peripheral seal ring.
The gas ejection valve is configured as described above, so that when an end of the valve pin is pushed from the outside of the gas container, the small-diameter portion is moved to a position of the inner peripheral seal ring where the large-diameter portion has been placed, producing a clearance between the inner peripheral seal ring and the valve pin to open the gas passage. This causes contents in the gas container to eject outside together with gas.
When applied, for example, to ejection containers for chemical agents for medical application, the gas ejection valve should be reduced in size, which requires the inner peripheral seal ring of several millimeters in diameter. It is thus practically difficult to accurately form a holder groove of the valve casing for receiving the inner peripheral seal ring by machining a single block of the valve casing. For this reason, the valve casing is conventionally composed of a plurality of blocks, which are machined separately and then assembled to form the holder groove.
Specifically, the first block placed on the outer peripheral side of the gas container is formed with a concave, with which the second block placed on the inner peripheral side of the gas container is engaged axially. An inner peripheral corner of the second block is cut annularly to form the holder groove between the first and second blocks. Specifically, the second block has an L-shaped section recess, two sides of which define a bottom wall and one side wall of the holder groove. An inner peripheral edge of the lower surface of the first block defines another side wall of the holder groove.
With the above gas ejection valve, however, since the holder groove for receiving the inner peripheral seal ring is defined by the plurality of blocks, high-pressure gas in the gas container acts not only on the inner periphery of the inner peripheral seal ring along the valve pin directly, but on the outer periphery of the inner peripheral seal ring through a mating face of the blocks. As a consequence, the inner peripheral seal ring is greatly deformed by the synergism of the gas pressures resulting from the two paths, resulting in potential slight leakage of gas in the gas container to the outside through the inner peripheral seal ring.
Particularly, when using high-pressure gas with higher permeability such as liquefied CO2 gas as a propellant, leakage of gas through the inner peripheral seal ring can be greater in consequence of long-term preservation, resulting in inconveniences such as undesired increase in concentration of contents ejected from the gas container and decrease in the longevity of the ejection apparatus.
It is, therefore, an object of the present invention to provide a gas ejection valve that is free from leakage of gas through a seal ring, and contributes to stable concentration of contents ejected from the gas container and increased longevity of the ejection apparatus.
The present invention generally provides a valve for a gas ejection apparatus with a container, comprising:
a casing secured to an opening of the container, the casing comprising first and second blocks that cooperate to define a first groove and have a first mating face formed with a space;
a pin movably held by the casing, the pin having a passage;
a first seal ring disposed on an inner periphery of the casing, the first seal ring being in close contact with an outer periphery of the pin, the first seal ring being received in the first groove,
wherein when the pin is pushed down, the passage ensures fluid communication between an outside of the container and a portion of the casing closer to an inside of the container than the first seal ring; and
a second seal ring received in the space, the second seal ring preventing fluid communication between the inside of the container and the first groove.
One aspect of the present invention is to provide an apparatus for ejecting gas, comprising:
a container with an imaginary axis; and
a valve hermetically mounted to the container, the valve comprising:
a casing secured to an opening of the container, the casing comprising first and second blocks that cooperate to define a first groove and have a first mating face formed with a space;
a pin movably held by the casing, the pin having a passage;
a first seal ring disposed on an inner periphery of the casing, the first seal ring being in close contact with an outer periphery of the pin, the first seal ring being received in the first groove,
wherein when the pin is pushed down, the passage ensures fluid communication between an outside of the container and a portion of the casing closer to an inside of the container than the first seal ring; and
a second seal ring received in the space, the second seal ring preventing fluid communication between the inside of the container and the first groove.
Another aspect of the present invention is to provide a valve for a gas ejection apparatus with a container, comprising:
a casing secured to an opening of the container, the casing comprising first, second and third blocks, the first and second blocks cooperating to define a first groove and having a first mating face, the first and third blocks having a second mating face, the second and third blocks having a third mating face, the first, second and third mating faces being formed with a space;
a pin movably held by the casing, the pin having a passage;
a first seal ring disposed on an inner periphery of the casing, the first seal ring being in close contact with an outer periphery of the pin, the first seal ring being received in the first groove,
wherein when the pin is pushed down, the passage ensures fluid communication between an outside of the container and a portion of the casing closer to an inside of the container than the first seal ring; and
a second seal ring received in the space, the second seal ring preventing fluid communication between the inside of the container and the first groove.
The other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.